advector

Synopsis

release massless particles into velocity field

Input Port

in_field	Mesh + Node_Data
in_probe	mesh of initial particle positions
in_glyph	Grid describing geometry of particle glyph
ui_parent	user interface parent object

Parameters

velocity vector	UIradioBoxLabel	selects which vector component to advect
N-segments	UIslider	accuracy of integration
Max Segments	UIslider	total number of integration steps
Order	UIslider	order of integration
Min Velocity	UIslider	minimum velocity value when integration stops
Direction	UIradioBoxLabel	forward/backward motion of particles
Mode	UIradioBoxLabel	render glyphs to represent data values
Glyph Normalize	UItogglemeone	normalizes glyph size
Glyph Scale	UIslider	scale factor for glyph
Start Time	UIslider	start of advection
End Time	UIslider	end of advection
Step	UIslider	integration step
Release Interval	Uislider	Time interval at which to release particles
Time	UIfieldTypein	current time value
Run	UItoggle	press to start/stop advection
Reset Time	UItoggle	reset time to Start Time
Cycle	UItoggle	on End Time, continue with Start Time

Output Port

out_fld	Mesh + Node_Data
out_obj	output renderable object

Description

advector releases a sample of zero mass particles into a field with a component that represents a velocity vector, for example, a fluid flow simulation. The particles have no initial direction or speed. The particles move through the velocity field according to the magnitude and direction of the vectors at the nodes in the volume. A forward differencing method is used to estimate the next position of each particle as a function of its current position and velocity.

Advection starts when you turn the Run toggle on. If you have set the Release Interval, another set of particles is released each time the specified interval passes.

Advection for individual particles stops when one of the following conditions occurs:

A particle exceeds the Max Segments value.

The particle's velocity drops below the Min Velocity.

The particle goes outside the field's bounds.

Advection of all particles stops when one of the following two conditions occurs:

The End Time value is reached.

You turn the Run toggle off.

Input

in_field

The input is any mesh with Node_Data. The first component is used and must be a scalar or a two- or three-element velocity vector. You can use extract_component before this macro to get the component you want out of a multi-component field.

in_probe

Any mesh whose coordinates represent the sample points. Meshes that are not unstructured are accepted, but a local unstructured version is generated during execution.

To create this sampling mesh you could use the plane object in Geometries.FPlane or the slice macro.

in_glyph

A Grid describing a glyph to represent the particles. This is simply a mesh describing the geometry of the glyph. Any mesh can be used (for example, that of a teapot), but for convenience you can use the Geometries objects to generate arrows or solid arrows, and so on

ui_parent

A port to connect to a user interface object that contains the macro's widgets. By default, it is connected to the default user interface object in the application in which the macro is instanced. (This default connection is not drawn.)

Parameters

velocity vector

UIradioBoxLabel. A radio box to pick which of the input field's components to use as the velocity vector. The selection can be a one-, two-, or three-element vector. The default is the first (0th) component. If node data labels are present, they are displayed.

N-segments

UIslider. An integer slider that sets the number of integration steps used within one grid "cell" to compute the streamline/particle path. The default is 2. The range is from 0 to 16.

Max Segments

UIslider. An integer slider that sets the total number of integration steps. When an individual particle exceeds this value, integration for it stops. The range is from 1 to 10000. The default is 256.

Order

UIslider. An integer slider that sets the order of integration. Higher orders are more accurate, but execute more slowly. The default is 2. The range is from 1 to 4.

Min Velocity

UIslider. A float slider. When a particle falls below this velocity, the integration process for that particle stops. The default is 0.00001. The range is from 0.0 to unbounded. You can use this to prevent wasted computation for particles barely moving, or even stationary (Min Velocity = 0).

Direction

UIradioBoxLabel. A radio box that controls whether particles are advected forward or backward from the starting sample points. The default is forward.

Mode

UIradioBoxLabel. A radio box that establishes how glyphs are rendered to represent the data values. (Glyphs are always colored by the magnitude of the data values in the component.) The choices are scalar, vector, or components:

scalar

Scale the glyph by the magnitude of the vector at that position.

vector (default)

Scale the glyph by the magnitude of the vector at that position. Also rotate the glyph in X, Y, (and Z) by the first, second, (and third) vector subcomponent values at that position. For example, a Cross3D in_probe would be rotated to reflect the vector values.

components

Scale the glyph in X, Y, (and Z) by the first, second, (and third) vector subcomponent values at that position. For example, a Cross3D in_probe's three lines would be individually scaled to match the vector values.

Glyph Normalize

UItoggle. If off, the sizes of the glyphs are proportional to the data component values at each node. If on, all glyphs are the same size. The default is off.

Glyph Scale

UIslider. A float slider to adjust the sizes of the glyphs. The default is 1.00. The range is 0.0 to 100.00.

Start Time

UIslider. A float. The time value along the original streamline continuum at which to start advection. (See DVadvect man page.) The default is 0.0.

End Time

UIslider. A float. The time value along the original streamline at which to halt advection of all particles. The default is 1.0.

Step

UIslider. A float. The value by which to increment the time along the original streamline continuum for each advection step. The default is 0.2.

Release Interval

The time interval at which to release another set of particles. The default is 0. If this parameter is 0, the module releases just one set of particles.

Time

UIfieldTypein. An output only widget that displays the current time in the count from Start Time to End Time.

Run

UItoggle. Starts or stops advection.

Reset Time

UItoggle. Reset Time to the value of Start Time.

Cycle

UItoggle. When End Time is reached, start the advection again at Start Time.

Output Port

out_fld

The output is a new unstructured Mesh composed of the original mesh plus the meshes representing the particles. Its new Node_Data element's values represent the selected velocity component.

out_fld1

This output field is a new unstructured mesh of cell type Polyline that represents the streamlines. Its new Node_Data contains the selected element's velocity component. The output also contains a reference to the input field's xform.

out_obj

This is a renderable version of the out_fld output field.

out_obj1

This is a renderable version of the out_fld1 output field.

Algorithm

advector uses precomputed streamlines (from DVstream) as particle paths. It integrates velocity along the streamlines to calculate the new position of the particles at each time step.
The streamlines are originally calculated using the Runge-Kutta method of specified order with adaptive time steps.

Example

Libraries.Examples.Visualization.Advect
v/dv_examp/advect.v

File

v/modules.v

See also related modules

streamline